CxF/X-4 is defined in ISO 17972-4 as a subset of the CxF Version 3.0 standard for exchanging color information. A CxF/X-4 file characterizes a particular spot color in conjunction with a print substrate by means of its spectral reflectance data. It also includes a wide range of metadata.

CxF/X-4 data can be embedded in PDF/X documents to effectively communicate the characteristics of the spot colors used in the file. See also ISO 32000-2.